1. Dyeing with fresh Japanese Indigo leaves (after Fischer and Yoshioka) This method requires only white vinegar and water. It works best on animal fibres producing a medium turquoise blue on wool and darker blues on silk. Before you start, fill some plastic bottles with water and put them in the fridge to cool overnight. Also put the fibre which you are going to dye, to soak overnight.
You need to work quickly after harvesting the leaves to prevent the unstable pigment from decomposing before it attaches itself to the fibres.
a) Cut or tear the leaves finely or put them in a blender or liquidiser, a handful at a time, with some cold water.
b) Pour the blended leaves into a plastic washing up bowl with chilled water and a little vinegar (I used two tablespoons of white vinegar for 250 g of leaves).
The acidity of the vinegar helps to release the pigment and to delay its breakdown.
Soak the leaves for about half an hour and then squeeze the blended leaf sludge hard to release the pigment.
c) Strain the leaves and save the liquid that has the colour of spinach. Put the leaves in another bowl with water and vinegar and repeat the procedure.
I strained the leaves with a fine sieve for this photo but some debris went through the sieve and it is better to strain the leaves through muslin or even some fine silk that you want to dye.
d) Add the fibre and leave it for an hour.
e) The fibre will first turn green and slowly change to blue. Take the fibre out of the dye bath and let it dry. Wash the fibre two days later.
f) You can repeat the procedure on the same material with fresh leaves for darker blues.
Further details of Yoshioka’s technique in Fischer’s article.
2. Indigo vat dyeing with the extraction vat & dithionite With 1 kg of Japanese indigo leaves you should be able to dye at least 500g of fibre. If you are using silk or wool, make sure it has been well washed; cotton needs to be well scoured beforehand. There is no need to mordant the fibre. Warm the fibre in water at a similar temperature to the indigo vat.
Heat the indigo vat in the saucepan to 50 °C. Sprinkle 4 teaspoons of dithionite on the surface of the vat (buy your dithionite here). Put the lid on the saucepan and keep the saucepan at 50 °C for an hour. This may be achieved by keeping the saucepan near a radiator, in a basin with hot water or by wrapping it with blankets.
Wearing rubber gloves, squeeze the fibre while still in the soak water, keep it squeezed (compression helps to keep the air out) as you let the excess water drip into the soak water. Lower the fibre into the dye vat and then release it. Leave for 10 min.
Remove fibre and expose to the air for 15 min. Rinse briefly. Dip fabric for 1 min and expose for 15 min. Repeat a few times. Leave to air overnight, or for 48 hours. Rinse well.
3. Indigo vat dyeing with fermented indigo leaves In Japan, the leaves are fermented for three months in a warm and moist atmosphere. This produces a substance similar to compost that is full of indigo. This indigo is used in fermentation vats buried in the ground which can produce very dark blues with repeated dippings.